With the advance of an information communication technology, various wireless communication technologies have been developed. Among them, a wireless local area network (WLAN) allows wireless Internet access in a specific service area (e.g., home, businesses, aircraft, etc.) by using a portable terminal on the basis of a radio frequency technique. Examples of the portable terminal include a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
Recently, with the increasing availability of WLAN facilities, users of a portable terminal such as a laptop computer can perform their works with improved mobility. For example, the users can participate in a business meeting by carrying their laptop computers from their desks to the place where the business meeting is held. In this case, the users can still read data or the like while maintaining access to a local network. In addition, even if a wired connection is not provided, the users can access to the Internet through a gateway or one or more modems equipped in the local network. Likewise, business travelers can access to their e-mail addresses by using their portable terminals without any particular difficulties to read received e-mails or to write and send e-mails.
In the initial WLAN technology, a frequency of 2.4 GHz is used according to the institute of electrical and electronics engineers (IEEE) IEEE 802.11 to support a data rate of 1 to 2 Mbps by using frequency hopping, spread spectrum, infrared ray communication, etc. With the recent development of the wireless communication technology, an orthogonal frequency division multiplex (OFDM) technique or the like is applied to the WLAN in order to support a data rate of up to 54 Mbps. In addition, the IEEE 802.11 has developed and commercialized a wireless communication technology or has currently being developing the wireless communication system. Examples of the wireless communication technology include quality of service (QoS) improvement, access point (AP) protocol compatibility, security enhancement, radio resource measurement, wireless access in vehicular environments, fast roaming, mesh networks, inter-working with external networks, wireless network management, etc.
In the IEEE 802.11, a basic service set (BSS) is a set of stations (STAs) successfully synchronized. In addition, a basic service area (BSA) is an area containing members of the BSS. The BSA may vary depending on a propagation property of a wireless medium. Thus, a boundary of the BSA is ambiguous to some extent. The BSS can be classified into an independent BSS (IBSS) and an infra-structured BSS. The IBSS constitutes a self-contained network and is not allowed to access a distribution system (DS). The infra-structured BSS includes one or more APs, DSs, etc., and generally uses the APs in all communication processes including communication between STAs.
In the initial WLAN communication procedure, it is required that data must be transmitted through the AP in the infra-structured BSS while not allowing direct data transmission between non-AP STAs. Recently, however, a direct link setup (DLS) between the non-AP STAs is supported to improve efficiency of wireless communication (e.g., IEEE 802.11e). Accordingly, in a BSS supporting QoS, i.e., in a QoS BSS (QBSS) including a QoS STA (QSTA) and a QoS AP (QAP), non-AP STAs can set up a direct link and perform direct communication not through the QAP but through the direct link.
A DLS protocol in an IEEE 802.11e WLAN environment is based on the premise that the BSS is the QBSS supporting QoS. In the QBSS, not only the non-AP STA but also the AP is a QAP (i.e., an AP supporting QoS). However, in most of currently available WLAN environments (e.g., IEEE 802.11a/b/g WLAN environment), the AP is a legacy AP not supporting QoS even if the non-AP STA is a QSTA (i.e., a STA supporting QoS). As a result, in the currently available WLAN environments, there is such a limitation in that even the QSTA cannot use a DLS service.
A tunneled direct link setup (TDLS) is a wireless communication protocol newly proposed to overcome the limitation above. The TDLS is proposed to allow QSTAs to set up a direct link in the currently available IEEE 802.11a/b/g WLAN environment not supporting QoS. In addition, the TDLS is proposed to enable a direct link setup even in a power save mode (PSM). Therefore, the TDLS defines all procedures or methods for allowing the QSTAs to set up the direct link even in a BSS managed by the legacy AP. A wireless network supporting the TDLS will be hereinafter referred to as a TDLS wireless network.
In the TDLS wireless network, a direct link setup method between two non-AP QSTAs needs to be defined first in detail. This is because, unlike in the IEEE 802.11e wireless network, the TDLS wireless network cannot allow an AP not supporting QoS to be directly involved in the direct link setup method between the non-AP QSTAs. In particular, to set up the direct link, a message for the direct link setup has to be exchanged between the non-AP QSTAs, and specific information on a peer non-AP QSTA, for example, a medium access control (MAC) address of the peer non-AP QSTA, is required. However, these requirements are not defined in detail in the DLS link setup procedure specified in the IEEE 802.11e or in a TDLS link setup procedure proposed up to now.